(257am) Evaluation of Infinite-Dilution Activity Coefficients and Vapor-Liquid Equilibria in the Region of Extremely Dilute Composition Using NRTL Equation

The vapor-liquid equilibrium data in the region of extremely dilute composition are very important for discussing the distillation separation in the region of dilute composition. The authors have published some articles on measurement of infinite dilution activity coefficients using ebulliometer. At those articles the authors measured the bubble points in the region of 10^-3 to 10^-1 mole fraction and made use of Ellis and Jonah model or equation for bubble point curve in order to obtain the terminal slopes of bubble point curves. The vapor-liquid equilibria were then obtained using Tao equation.

This article deals with the measurement of bubble points (x-T-P) at alcohol compositions 10^-5 – 10^-2 mole fraction for methanol + water and ethanol + water using new type ebulliometer. The total pressure is 101.3 kPa. The infinite-dilution activity coefficients and vapor-liquid equilibria have been determined using experimental bubble points and conventional methods.

On the other hand, NRTL equation has been used widely in order to calculate vapor-liquid equilibria from the practical point of views. The infinite-dilution activity coefficients and vapor-liquid equilibria evaluated using NRTL equation with bubble point data in the region of extremely dilute composition have been compared with those values using the conventional method for seven binary systems.